Turbins De Gas

European Congress on Computational Methods in Applied Sciences and Engineering ECCOMAS 2004 P. Neittaanm¨ki, T. Rossi, S. Korotov, E. O˜ ate, J. P´riaux, and D. Kn¨rzer (eds.) a n e o Jyv¨skyl¨, 24–28 July 2004 a a

DESIGN OF GAS TURBINE ENGINES USING CFD
Leigh Lapworth and Shahrokh Shahpar
Aerothermal Methods Group Rolls-Royce plc, P.O.Box 31, Derby, DE24 8BJ, England e-mails:leigh.lapworth@rolls-royce.com, shahrokh.shahpar@rolls-royce.com web page: http://www.rolls-royce.com

Key words: Turbomachinery, Design, Optimisation, Adjoint. Abstract. This paper describes a general purpose design system being developed at RollsRoyce plc. The key elements of the system are a parametric design and rapid meshing capability; a state-of-the-art CFD solver with an adjoint capability; and, anadvanced optimisation system consisting of a library of optimisers. A description is given of each element in the design system. To illustrate its use and flexibility, five different applications of the system to a gas turbine are described. These are: optimisation of the guide vanes in the bypass duct to minimise excitation of the fan rotor; the same bypass guide vane optimisation using sensitivitygradients from the adjoint solver; optimisation of a compressor stage to improve efficiency whilst constraining flow rate, pressure ratio and outlet flow angle; minimisation of the forced excitation of a turbine rotor by modifying the wake of the upstream nozzle guide vane; and, optimisation of a fan rotor to reduce tone noise.

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Leigh Lapworth and Shahrokh Shahpar

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INTRODUCTION

Thedesign of individual gas turbine components using CFD is now commonplace [1]. Traditional design by analysis methods are increasingly being supplemented with automated design systems [2] and the use of optimisation systems [3]. At the same time, fluid machinery can now be modelled and analysed to an unprecedented level using CFD on powerful multi-processor computers or clusters. Although CFD canprovide essential information to aid the physical understanding of complicated flow fields, it is generally the requirement to design/modify geometry that drives the application of CFD. When applied to an individual component, the physical understanding gained from CFD is often able to guide design improvements to that component. However, fluid machinery is generally characterised by the interaction of anumber of components, such as multistage turbomachinery; the intake and the fan rotor; the combustor and the upstream diffuser; and, so on. A truly optimal design can only be achieved by accounting for all the component interactions. It is here that the design by analysis approach becomes limited - a designer may know how he/she would like to change the flow field, but changing the geometry toachieve that is much less intuitive than in single component design. If the requirement to meet a number of constraints is added, then design by analysis becomes a very crude tool. This paper describes an automated design system that has been developed specifically with multi-component fluid machinery in mind. Section 2 describes the main elements of the design system. Section 3 describes five novelapplications of the system. 2 ELEMENTS OF THE DESIGN SYSTEM The design systems consists of the following processes: • Parametric representation • Geometry construction • Mesh generation • CFD solution • Data extraction and functional evaluation • Optimisation The systems that implement these processes are described in the following sections. An underlying theme of all the systems is that they have abatch execution mode that allows them to be run automatically by the optimiser.

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Parametric representation

Although the parametric representation, geometry construction and mesh generation are logically separate processes, they are intimately linked with the objective of creating a CFD mesh in the shortest possible time. With this in mind, an...